Innervation question

[DistantMets]

Maybe this is a dumb question...

My references always list medial gastroc as S1, S2 innervated.

An attending of mine considers it L5, S1, S2 and since I have seen it in some other references.

This kinda screws up my routine. I liked thinking of it as S1, S2 because I have plenty of other good L5 muscles to stick. Am I ok or is the lateral gastroc a better pure S1, S2?

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[Ludicolo]

I’ve seen both the MG and the LG listed as either L5-S1-S2 or S1-S2 in various sources as well. I was taught S1-S2 for MG and L5-S2 for LG. I consider them both predominantly S1 innervated, with the MG leaning a little toward S2, and the LG leaning a little toward L5. I needle the soleus if I’m thinking S2.

 

[topwise]

Wow, we were *just* having a discussion about this yesterday.

Most places I've seen say that the medial gastroc is S1, S2. And lateral is L5,S1. But I bet it's one of those things that might vary person to person.

 

[RUOkie]

There is a tremendous amount of anatomical variation in the lower extremities with innervation. That is why AANEM recommends needling plenty of muscles.

 

[DOctorJay]

This is from our EMG material at Mayo

Gastrocnemius lateral
Tibial
L 5 S 1 2

Gastrocnemius medial
Tibial
S-1 2

 

[Ludicolo]

This is from our EMG material at Mayo

Gastrocnemius lateral
Tibial
L 5 S 1 2

Gastrocnemius medial
Tibial
S-1 2

From Perotto (3rd edition):

Lateral gastroc S1, S2 (later on comments that it is involved in lesions of L5,S1,S2 roots)

Medial gastroc S1, S2 (also comments that it is involved in lesions of L5,S1,S2 roots)


From Geiringer (2nd edition):

Lateral gastroc S1, S2

Medial gastroc L5,S1,S2


From Dumitru (2nd edition):

Lateral gastroc L5,S1

Medial gastroc L5,S1,S2


From Brown and Bolton (2nd edition):

Lateral gastroc L5,S1

Medial gastroc S1,S2

 

[Ludicolo]

There is a tremendous amount of anatomical variation in the lower extremities with innervation. That is why AANEM recommends needling plenty of muscles.

They do?

 

[DistantMets]

I routinely needle TFL, VMO, TA, PL, Med Gastroc.

If paraspinals + TFL + TA + PL neuropathic with nl MG then I would normally call L5
If paraspinals + TFL + PL + MG neuropathic with nl TA then I would normally call S1

The question would be if TA, PL & MG are positive...is it L5 and S1, just L5, or L5/S1 undifferentiated? I guess I should probably needle a foot muscle like AH since it definitely should not have any L5? I thought about FHL as well since I didn't find any references listing L5. I also like H-reflexes to help me decide if S1 is involved.

 

[SSdoc33]

save yourself the headache. just call it S1

 

[PMR 4 MSK]

This is probably one of the reasons I see EMG reports from other docs saying Radiculopathy L5-S1. They see changes in gastroc and tib ant and say it must be a polyradic. It can often be teased out if you do more muscles and keep variability in mind.

 

[avatar]

I routinely needle TFL, VMO, TA, PL, Med Gastroc.

If paraspinals + TFL + TA + PL neuropathic with nl MG then I would normally call L5
If paraspinals + TFL + PL + MG neuropathic with nl TA then I would normally call S1

The question would be if TA, PL & MG are positive...is it L5 and S1, just L5, or L5/S1 undifferentiated? I guess I should probably needle a foot muscle like AH since it definitely should not have any L5? I thought about FHL as well since I didn't find any references listing L5. I also like H-reflexes to help me decide if S1 is involved.

In addition to the muscles above,I would add the biceps femoris (long head) which is a good S1 that I i do routinely for my radic screens. if I am having difficulty deciding between L5/S1, I will needle the medial hamstrings (more L5) and glut max (more S1). For feet, there is that unresolved issue of whether spontaneous activity can occur normally, but I do like AH.

 

[DistantMets]

Thanks for your feedback everyone. I guess I just need to keep in mind the gastroc can have some L5 in it. The more I do these, the more I realize I need to work quickly through the NCSs to leave time to needle a couple extra muscles to confirm my Dx.